As a hydraulic circuit for accelerating extension of a rod of a hydraulic cylinder, an acceleration circuit is known. For example, if the accelerating circuit is used for the hydraulic cylinder of a crusher, extension of the rod is accelerated to speed up a closing operation of a movable jaw. In the acceleration circuit disclosed in Patent Document 1, an inversion cylinder (an accelerating cylinder) is interposed between an actuating cylinder and a pump. According to this configuration, by interposing the inversion cylinder, the flow rate of oil supplied to the bottom side of the actuating cylinder is increased more than the flow rate of oil supplied from the pump to accelerate the extension of the rod of the actuating cylinder. This speeds up the closing operation of the movable jaw and reduces the operation time for crushing.
In the acceleration circuit of Patent Document 1, however, although the flow rate of oil supplied to the actuating cylinder increases, the oil pressure reduces and the thrust of the actuating cylinder decreases. Therefore, in a loaded condition, oil is directly supplied from the pump to the actuating cylinder by switching the circuit with a switch valve to exert the intrinsic thrust. In other words, the acceleration circuit of Patent Document 1 configures a function-selecting mechanism that switches priority between flow rate and thrust as described in Patent Document 1.